This invention relates to seating systems in general and, more particularly, to a self-adjusting pneumatic seating system useful in vehicles, aircraft, offices and homes.
Through the millennia since man became a biped he has sought ways to be comfortably seated, progressively advancing from suitable rock formations to hewn and shaped materials. With the growth of civilization, fashion soon took precedence; aesthetically more attractive chairs were produced often with a corresponding compromise in comfort. The problem has been exacerbated in modern times in two respects: first, of the numerous seating options available for purchase, many are little more than sculptures with aesthetic value without regard for function or its potential benefit or liability to the user, and, second, between driving, office work, reading and watching television, modern society has become primarily a seated population. As a consequence tens of millions of people experience back problems with attendant lost time at work and discomfort at home, coupled with medical expenses. Additionally, some available seating systems, particularly in the automotive field, offer so many optional settings that the result is confusion which may actually increase the potential for increased musculoskeletal stress by incorrect settings. It is very difficult for the seated user to determine his or her spinal profile and to subjectively balance the spinal support mechanism to match his or her needs.
Improvements in seating have been made in recent years as a result of awareness generated by research into back problems and biomechanical analysis of the musculoskeletal system. The vertebral column comprises four functional parts: from top to bottom, cervical, thoracic, lumbar and sacrum. The cervical and lumbar portions are the most mobile, the thoracic relatively immobile and the sacrum, which is almost completely fixed to the pelvis, is immobile. When a person is standing, the vertebral column forms a compound curve comprising the cervical lordosis, thoracic kyphosis and the lumbar lordosis. Pelvic rotation influences the lumbar curvature; forward pelvic rotation increases the lumbar lordosis while backward pelvic rotation tends to flatten or even create a lumbar kyphosis, a condition that often occurs when a person is sitting. Research has shown that there is a wide variation in the thoracic and lumbar curves of normal spines, which must be accommodated in a flexible seating system. Because of the structural rigidity afforded by the rib cage, the thoracic zone generally needs accommodation to the existing profile, whereas the lumbar zone, on the other hand, requires not only substantial accommodation but adjustment because of its wide articulation capabilities that can result in high musculoskeletal stresses when improperly supported. Therefore, proper spinal support for a person in a seated position is an important component of one's health. Proper seating is particularly important to the many who work in offices, drive vehicles, fly aircraft or engage in other occupations requiring being seated for long periods of time.
Among recent advancements in seating technology is the active biomechanical seating system described in U.S. Pat. No. 4,944,544 by Gross and applicant Santos wherein the spinal profile of an individual is encoded on a device which, upon insertion into an electronic module, causes the seat back to conform to the standing spinal profile of that individual. Since spinal disc pressures are normally at their minimum when the individual is standing, by approximating that profile when the individual is seated theoretically should be beneficial to health by virtue of maintaining minimal disc pressures. However, by so doing, comfort is compromised by imposing the encoded standing profile on the spinal zone. It appears that the numerous muscle and ligament layers in the pelvic region are unduly stressed due to the average 28.degree. pelvic rotation when a person is in a seated position.
While the theory advanced in the aforementioned patent may be applicable for high stress, very short duration seating in aerospace applications to avoid injury under high "G" forces, in situations requiring the individual to be seated for longer time periods it often is necessary to shift body position in an attempt to reduce musculoskeletal stresses on particular body components around the pelvic and lumbar areas. The described prior art system does not accommodate for such shifts in position, or slouching, except with the actuation of a manual override to compensate for such changes.
The pivot point of an adjustable seat back of a seating system averages seventeen centimeters from the pivot point of the ischial tuberosities about which the upper body rotates while seated. Changing the angle of the seat back relative to the seat pan completely changes the relationship of the spine of the seated individual to the support profile of the backrest due to the different curves defined by the different axes of rotation. Both the lordotic curve and the apex of the curve assume different positions relative to the seat back, and a slouched position compounds the problem of proper support. Under any of these conditions a presupposed and predetermined seat back support profile becomes incorrect; that is to say, in each of these cases the accuracy of the encoded spinal data settings or predetermined seat back profile is severely jeopardized.
Another deficiency of this and other known seating systems is that cushioning materials such as foams used on the backrest in most seating systems do not conform to the natural spinal curve of a person since cushion deformation is basically a non-linear function of applied force. The result is the generation of pressure points along the spinal column and adjacent musculature. Seating systems in which cushioning materials are combined with static, mechanical or pneumatic single lumbar supports provide maximum comfort levels for only a fraction of the population close to the fiftieth percentile with the result that the comfort of the rest of the population is compromised.
A primary object of the invention is to provide a new and improved spinal support device which eliminates the foregoing disadvantages of prior art seating systems.
It is another object of the present invention to provide a seating system for providing a seated individual customized spinal support with little or no adjustment of the seat back.
A more specific object of the invention to provide a new and improved pneumatic spinal support device which balances the forces exerted by the seat back on elements of the spine and avoids creation of pressure points.
Another object is to provide a spinal support device in the seat back of a seating system which automatically adjusts the curvature of the seat back to the spinal curvature of the occupant of the seating system.
Another object of the present invention is to provide a new and improved pneumatic spinal support device which is comparatively simple in construction and economical to manufacture.